Double phase comparator circuit



July 31, 1951 w. J. OBRIEN DOUBLE PHASE COMPARATOR CIRCUIT Original Filed Aug. 27, i945 IN V EN TOR.

m m 0 J M M M Patented July 31, 1951 DOUBLE PHASE COMPARATOR CIRCUIT William J. OBrien, London, England, assignor to The Decca Record Company, Limited, London, England, a corporation of Great Britain Original application August 27, 1945, Serial No. 612,991. Divided and this application January 18, 1949, Serial No. 71,425. In Great Britain August 23, 1945 7 Claims.

My invention relates to a phase discriminator circuit for use with radio frequency receiving apparatus and suitable phase displacement indicators for indicating the phase relationships between synchronized radio frequency transmissions from spaced antennae and at unlike but related frequencies.

This application is a division of my copending application Serial No. 612,991, filed August 27, 1945, now Patent 2,500,200, issued March 14, 1950, and entitled Multiple Channel Radio Frequency Receiver.

As is disclosed in my 'copending application Serial No. 612,987, filed August 27, 1945, now abandoned, and entitled Navigation System it is possible by means of synchronized radio frequency transmissions from spaced points and at unlike but related frequencies to establish superimposed and intersecting lines of equal phase displacement, thus defining a coordinate system which may be used for guiding the navigation of vehicles of various types. The utility of such a system depends, of course, upon equipping the vehicle with reception apparatus suitable for receiving the three synchronized transmissions and for indicating the relative phase relationships between these transmissions in terms of the coordinate system developed by the overlapping and interacting radio frequency fields. Such an apparatus must include the necessary instrumentalities for simultaneously receiving the three signals, for making a phase analysis and comparison of the signals, and indicating on a suitable instrument the result of the analysis and comparison in terms of the established coordinate system.

It is, therefore, an object of the present invention to provide a radio frequency receiving apparatus which includes means for receiving simultaneously three separate but related radio transmissions, together with means for analyzing, comparing and indicating the phase relationships existing among the respective transmissions.

It is an additional object of my invention to provide 'an apparatus of the character set forth in the preceding paragraph in which the phase relationship indication is given continuously.

Other objects and advantages of my invention will be apparent from a study of the following specifications, read in connection with the accompanying drawing, wherein:

Fig. 1 is a. schematic drawing representing the elements of a radio frequency navigation system of the character disclosed in my aforementioned copending application Serial No. 612,987 with which the radio reception apparatus to be described hereinafter is particularly adapted for use; and

Fig. 2 is a wiring diagram illustrating in detail the components and electrical connections employed in the phase discriminator circuit.

Referring to the drawings, I have illustrated in Fig. l a radio frequency navigation system of a type with which the radio receiving apparatus may be used. As is described in my aforementioned copending application Serial No. 612,987, the transmission apparatus may include three radio frequency transmitters A, B and C. In the event the apparatus is to be used for guiding the navigation of sea-going vessels, such as is represented in Fig. 1 by the outline I, the transmitters A,'B and C may be placed at or near the shoreline 2. They are spaced from each other at predetermined distances and are synchronously operated at unlike but related frequencies as, for example, 60, and kilocycles, respectively.

With this mode of operation, the radio frequency fields produced by transmitters A and B interact to establish a field pattern such as that represented by the solid lines 3 in Fig. 1, each of which lines represents the locus of the equal phase displacement between the signals emana'ting from the transmitters A and B and referred to a 'frequencywhich is the least common multiple of the frequencies "at which the transmitters are operated as, for example, a frequency of 240 kilocycles. Similarly, the interaction of the fields produced by the transmitters A and C may be characterized by lines 4 of equal phase displacement as referred to a frequency equal to the least common multiple of the two transmission frequencies; in the example assumed, kilocycles. 1

Suitable radio frequency apparatus is installed on the vessel I and connected to a suitable antenna 5 mounted thereon, The receiving apparatus operates indicating mechanisms for indicating the phase relationships between the A and B transmissions and the phase relationships between the A and C transmissions to thereby provide an indication of the geographical location of the vessel l in terms of the coordinate system represented by the equal phase displacement lines 3 and 4.

The receiving apparatus is preferably constructed along the lines described in my aforementioned copending parent application Serial No. 612,991, now Patent 2,500,200, and may comprise three radio frequency amplifiers tuned respectively to the frequencies radiated by the transmitters A, B and C (60, 80 and 90 kilocycles in the assumed example). The 80 and 90 kilocycle amplifiers are connected to a frequency trebler and a frequency doubler, respectively, to produce output signals of 240 kilocycles and 180 kilocycles. The output from the 60 kilocycle amplifier is split and fed into a frequency 'quadr'upler and a frequency trebler to produce outputs of 240 kilocycles and 180' kilocycles. There are thus pro= duced two 240 kilocycle signals derived from transmitters A and B, and two 180 kilocycle sig nals derived from transmitters A and By measuring the phase relation between the two 240 kilocycle signals, and the phase relation between the two 180 kilocycle signals, there is provided an identification of the lines 3 s at (Fig.1) which pass through the location of the receiving antenna 5.

I have shown in Fig. 2 a phase discriminator circuit which may be advantageously'used for making the phase measurement. While I have shown but one of the phase discriminator cir= cuits; it will be understood that two such circuits are used, one for determining the phase relation between the two 240 kilocycle signals and the other for measuring the phase relation of the two 180 kiloc'ycle signals. It will be understood also that the two circuits are identical except for the difference in tuning of the resonant circuits. Each discriminator includes two pair of input terminals 33, 34 and 45, 46 across which are applied respectively the two signals, the phase rela-' tionship of which is to be determined.

The input terminals '33 and 34 are connected to atransformer primary winding55 which is closely coupled to a secondary winding 51 tuned by a tuning condenser 59. Another secondary winding 58 isloosely coupledto the secondary winding 51-. The winding 51 is loaded by a shunt resistance 6|, whereas the winding 58 is connected through a series resistance Gla to a tuning condenser 60. The inductance of the winding 58 is made slightly greater than that of the winding 51, and the coupling is adjusted to produce equal voltage outputs acrossthe condensers 59 and 60, respectively, and arealso so adjusted as to pro-'- duce a'pha'se difference between these voltages of precisely 90. The condensers '59 and 60 are chosento tune the two windings to the same frequency as that applied'across terminals 33 and 34. The loading resistances 6| and Bliz are employed to reduce the Qof the tuned circuits to improve thefr'e'tiuency shift tolerance of thee-ir c'uits.

@ne terminal of the condenser 60 "is'co'nnected as by means of conductors B2 and 63 to the plates or anodes of'thermionic rectifier tubes T1 and T2. The cathodes of these two tubes are intercon nected by four series connected resistors 54,55, '53 and 51, the mid point between resistances "65 and being connected through conductor "68 to the other terminal of the condenser '69.

The resistances '95 and 66 are-preferably bypassed by condensers 69 and 10 and the mid point between resistances 6E and65 is grounded as by a conductor H. Therrnionic rectifier tubes T3 and T4 with cathode resistances ll, 13, 14 andf'l5 are connected across the transformer winding 51 in a manner identical to the circuits associated with the winding 58. Inputtermi'n'als 45 and '46 are'connected across a primary winding 16 of an input transformer 11 inductively coupled to a'seoondary winding '18 thereof.

The winding 18 is preferably provided with a cehtertap which isconnected to ground as by a conductor 19'and the windings Wand [8 are 4 tuned to the input frequency as by tuning condensers 80 and BI. The windings l6 and 1B are loaded respectively by shunt connected resistances 16a and 18a, these resistors being employed for the purpose of reducing the Qof the tuned circuits. The secondary winding 18 is so constructed as to provide a voltage across these terminals equal to that appearing across the terminals of the secondary winding 51. One terrhinal of the winding 18 is connected through conductors 82, 83 and coupling condensers 84 and B5 to the cathodes of the rectifier tubes T2 and T4. The other terminal of the winding 18 connected through conductors 86 and 81 and coupling condensers "88* and '89 to the cathodes of the tubes T1 and Ts.

The mid point between resistances B6 and 61 is connected by a conductor 90 to the grid of an amplifier tube 9| and a similar connection interconnects the grid of an amplifier tube 92 to the mid point between resistances "l4 and 15'. These grid leads include series resistances 9la-and92u which, together with grid to ground condensers 9Ib and 92b, serveto filter out noise and other extraneous signals to prevent the fluttering of the needle of a goniometer 52 which is driven by the tubes 9| and 92. The anodes of the tubes 9! and 92, are interconnected and connected to a'suitable source of plate supply potential represented by the arrow bearing the legent 13+ in Fig. 2. The cathodes of the tubes9l and-92 are interconnected by a series circuit including resistances 93, 94, 95 and 96 the mid point between resistances 94 and 95 being connected to a suitable source of direct potential having a negative polarity with respect to ground and indicated generally by the arrow bearing thelegend C- in Fig. 2.

The mid point between resistances 93 and 94 is connected through a conductor 91 to one terminal of one coil 98 of the goniometer 52, the other terminal of said coil being connected to ground by a conductor 99 Similar1y,-the mid point between resistances-95 and 9G is connected by a conductor I00 to one terminal of the other coil Illl of the goniometer 52, the other terminal of said coil being connectedto ground through a conductor [02.

In the phase discriminator circuit just -de-- scribed, the voltage which is applied across the tube T1 is the vector sum of the voltage across the winding -53 and "the voltage on centimeter 86. The voltage'applied to the tube 'Ta is me vector sum "of the voltagedeveloped across the" winding '58'and"the='voltage on 'onductbr 9 In alik'e'manner,'thevoltage "acro'ss the tube the vector sum of the voltage developed-across the winding'51'andthatappearingon condu o 86, while the voltage acrcss th'e tube This he vector "sum 'of the voltage devm ed across 'tih'e ETand'tlie voltage dnecneucttr sz. 1

The voltages developed across thewindings "51' shuts Iisti'tute one system-sf a (1 phase quadrature relationship; hereas tn voltages on conductors "$2 anddli 'esmpnsea independent system which the tbltag'estfe -1 fiXedspec;

four tubes T1-T4* inputpliasjerelaticns p varies.

The direct cenent nciving si a" "BiQQdfEF-"GL direct'proporticn to the v0 oug h the re p use a nea-across the four tubes and therefore represent by their magnitude the phase relationship between the incoming signals. A portion of each of these volt-,- ages is applied to the grids of the amplifier tubes 9| and 92 so that thecurrent flowing in the cathode circuits of these tubes and therefore through the goniometer coils 98 and HH are 'in a ratio substantially equal to the tangent of the phase angle between the input signals.

The goniometer coils 98 and I! are disposed at right angles to each other in the goniometen The magnetic flux produced by the. interaction of these coils has a direction which is determined by the vector sum of the two coil currents disposed at right angles to eachother. The direc tion of the resultant field is therefore representative of the phase angle between theinput signals. An indicator 53 forming a part of the goniometer 52 is attached to a permanent magnet mounted for rotation in the resultant magnetic field and the pointer therefore assumes a position representing the phase relationship between the input signals.

- The goniometer 52 is preferably of the registering type such as that disclosed in my copending application Serial No. 612,984, filed August 2'7, 1945, now Patent 2,499,326, issued February 28, 1950, and entitled Registering Goniometer, and which is adapted to indicate, as by a suitable pointer 53, the instantaneous phase relationship. An associated registering mechanism (not shown) connected by suitable gearing to the pointer 53 serves to indicate the accumulative total of phase changes occurring during the time the device is in operation. Assuming, therefore, that the registering mech-. anism of the indicating instrument 52 was initially set to indicate a coordinate location equivalent to the geographical location of the vessel i, the instrument will continuously operate to indicate the instantaneous location of the vessel I with respect to the equi-phase grid represented by the dotted lines 4. A similar instrument connected to the output of a second phase discriminator will indicate the position of the vessel 1 with respect to the equi-phase grid 3. Together, the two indicators continuously indicate the location of the vessel 1 From the foregoing it will be seen that I have provided a novel phase discriminator and phase displacement indicator for use with suitable receiving and frequency converting apparatus to indicate the multiple phase relationships between synchronized radio frequency transmissions from spaced antennae and at unlike but related frequencies.

While I have shown and described the preferred embodiment of my invention, I do not desire to be limited to any of the details of construction shown and described herein, except as defined in the appended claims.

I claim:

1. In a phase discriminator circuit for determining the phase angle between a first and a second input signal of a given radio frequency, the combination of: means for producing a third signal of said given frequency and bearing a fixed phase quadrature relation to said first input signal; means for producing a fourth signal of said given frequency and bearing a fixed phase opposition relation to said second signal; two pair of rectifiers; a load resistance for each of said rectifiers; circuit means for applying to the respective rectifiers of one pair the vector sums of said first input signal plus said fourth signal and said first input signal and said second input signal; circuit means for applying to the respective rectifiers of the other pair the vector sums of said third signal plus said fourth signal and said third signal plus said second input signal; and circuit means for each of said pairs of rectifiers for effecting an algebraic addition of the direct potentials produced across the load resistances thereof, whereby the two resulting direct potentials bear the same magnitude relation to each other as exists between the right angle components of said phase angle.

2. In a phase discriminator circuit for determining the phase angle between a first and a second input signal of a given radio frequency, the combination of: means for producing a third signal of said given frequency and bearing a fixed phase quadrature relation to said first input signals; means for producing a fourth signal of said given frequency and bearing a fixed phase opposition relation to said second signal; two pair of rectifiers; a load resistance for each of said rectifiers; circuit means for applying to the respective rectifiers of one pair the vector sums of said first input signal plus said fourth signal and said first input signal and said second input signal; circuit means for applying to the respective rectifiers of the other pair the vector sums of said third signal plus said-fourth signal and said third signal plus said second input signal;-

circuit means for each of said pairs of rectifiers for effecting an algebraic addition of the direct potentials produced across the load resistancesthereof, whereby the two resulting direct potentials bear the same magnitude relation to each other as exists between the right angle components of said phase angle; and a permanent mag-i 3. In a phase discrminator circuit for deter-' mining the phase angle between a first and a secand input signal of a given radio frequency, the combination of: means for producing a third signal of said given frequency and bearing a fixed phase quadrature relation to said first input signals; means for producing a fourth signal of said given frequency and bearing a fixed phase opposition relation to said second signal; two pair of rectifiers; a load resistance for each of said rectifiers; circuit means for applying to the respective rectifiers of one pair the vector sums of said first input signal plus said fourth signal and said first input signal and said second input signal; circuit means for applying to the respective rectifiers of the other pair the vector sums of said third signal plus said fourth signal and said third signal plus said second input signal; circuit means for each of said pairs of rectifiers for effecting an algebraic addition of the direct potentials produced across the load resistance thereof, whereby the two resulting direct potentials bear the same magnitude relation to each other as exists between the right angle components of said phase angle; and a permanent magnet goniometer connected to said last-named circuit means to effect a vector addition of the two components represented by said resulting direct potentials to thereby indicate the direction of their resultant representing said phase angle, said goniometer including a registering mechanism for indicating the algebraic sum of phase angle changes exceeding a full electrical circle.

eases '4. a phase discriminator circuit for =deter= mining the phase angle between a first and a second input signal ofla given radiofrequency, the combination of means for producin a third signal 'of said given frequency and bearing a fixed phase quadrature relation to said first input sig= rials; means for producing a fourth signal of said given frequency and bearinga fixed phase opposi tion relation to-said second signal; two pairs of rectifiers; a load resistance for each of said rec tifie'rs; circuit means for applying to the respec-' tive rectifiers of one pair the vector sums of said first input signal plus said fourth signal and said first input signal and said second input signal; circuit means for applying to the respective rec tifiers of the other pair the vector sums of said third signal plus said fourth signal and said third signal plus said second input signal; circuit means for each of said pairs of rectifiers for ef footing an algebraic addition'of the direct poten tials produced across the load resistances there-- of to produce a pair of resulting potentials; a pair of magnetic field windings disposed at right angles to each other; a permanent magnet mounted for pivotal movement into alignment with the resultant field produced by said windings; and means for applying to said windings respective potentials proportional to said result ing potentials, whereby said phase angle is indicated by the angular position of said permanent magnet.

5. In a. phase discriminator circuit for determining the phase angle between a first and a second input signal of a given radio frequency, the combination of: means for producing a third sigml of said given frequency and bearing a fixed phase quadrature relation to said first input signals; means for producing a fourth signal of said given frequency and bearing a fixed phase opposition relation to said second signal; two pairs of rectifiers; a load resistance for each of said rectifiers; circuit means for applying to the respective rectifier of one pair the vector sums of said first input signal plus said fourth signal and said first input signal and said second input signal; circuit means for applying to the respective rectifiers of the other pair the vector sums of said third signal plus said fourthsignal and said third signal plus said second input signal; circuit means for each of said pairs of rectifiers for effecting an algebraic addition-oi the direct potentials pro-- duced across the load resistances thereof to pro duce a pair of resulting potentials; a pair of mag= netic field windings disposed at right angles to each other; a permanent magnet mounted-for pivotal movement into alignment with the re= su1tant field produced by said windings; means for applying to said windings respective poten= tials proportional to said resulting potentials, whereby said phase angle is indicated by the angular position of said permanent magnet; and a registering mechanism coupled to said magnet for indicating phase angle changes exceeding a full electrical circle;

6; A phase comparator for indicating the phase difference between two alternating curre t Sig-f rials comprising a first and a second phase disfimina'ting Circuit, each including a pair of line ear i 'ctifii's for producing a pail Of output te'iitials' representati e respectively of the sine and cosine of the angle of said phase difference,- and an electromechanical means operated by said output potentials to provide a mechanical movement which is substantially linear with re-- pect to phase difference and having a direction of movement which is indicative of an increas ing or decreasing phase difference.

7. A phase comparator as set forth in 'clain'i fi which includes circuit means for applying to each of said linear rectifie'rs a differentcombination signal derived from both of said alternating cur-'1 rent signals, said combination signals being dif= ferent combinations of one of said alternating current signals, a signal of opposite phase to said one alternating current signal, the other of said alternating current signals, and a signal at phase quadrature to said other alternating cur rent signal.

WILLIAM J. OBRIEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES "FATENTS Number 

